From what I can tell, just by trying the script out, is that it doesn't work even on the demo page. The script either needs updating, or Google is simply no longer supporting it. It also looks to me as though Google never officially supported this script. If so, any past support was then strictly accidental.

1. I just looked at the script, it works off of the document.referrer property of the page, and Google appears to still be giving out an informative document.referrer. So it must be somewhere in the use that the script makes of this property that things are slipping up.

2. I just looked at the page's source code, and it appears as though the script isn't on it and there is no external script tag on the page for the script either. No wonder the demo page doesn't work.

3. I just tried out this script on a site I master, it works as per the Demo page's instructions. So this isn't really a bug in the script or its instructions, rather a bug in the demo page. If you need more help installing the script properly, post a new thread in the help section.